text: Besides the experimental study, it is important to have a good thermodynamic model to describe and predict liquid-liquid equilibrium conditions in engineering and design. To obtain global and reliable parameters for thermodynamic models usually, phase equilibrium data is suitable for this purpose. As there are polymer, electrolyte and water in polymer/salt systems, all different types of interactions should be taken into account. Up to now, several models have been used such as NRTL, Chen-NRTL, Wilson, UNIQUAC, NRTL-NRF and UNIFAC-NRF. It has been shown that, in all cases, the mentioned models were successful in reproducing tie-line data of polymer/salt aqueous two-phase systems. In most of the previous works, excess Gibbs functions have been used for modeling.